This is one of those areas where being an absolute geek can really help. No, it won't help you figure out what to say to them, but it can help you remember to do it at all. How?
The basic concept is very much like a "tickler file". (I'll wait while you go look at that article, if you're not familiar with them already.) The geeky twist I add, is that I don't file an actual physical document, just a reference in a spreadsheet.
Yes, a spreadsheet. They're not just for suits and green-eyeshades. They're a great way to organize any kind of information that you just need to record a few brief pieces of information about, and may need to sort in various ways.
Let's look at a small simulated excerpt from my client-hunting spreadsheet, which originally started as a job-hunting spreadsheet. (The company names have of course been changed. The dates are in YYYY-MM-DD format, aka ISO 8601, so that even if they're not in a "real" spreadsheet program, but rather a plain text file, they'll still sort in the right order.)
|Company||Status||Last Contact||Followup On|
|Fubar Heavy Industries Inc.||CALL THEM ASAP||2012-10-04||2012-10-08|
|Conceptual Concepts Ltd.||waiting for NDA||2012-10-03||2012-10-10|
|Widgets R Us||I emailed them||2012-09-28||2012-10-12|